Benjamin Herrenschmidt wrote:
> On Thu, 2008-12-04 at 06:51 -0700, Gary Thomas wrote:
>> I have a MPC5200 based board which has an FPGA for external
>> I/O, etc. This FPGA also funnels interrupts from the various
>> external devices through to the CPU.
>>
>> I've defined this structure in my DTS:
>>
>> [EMAIL PROTECTED] {
>> device_type = "board-control";
>> #address-cells = <1>;
>> #size-cells = <1>;
>> // Note: includes sub-devices like CAN, A/D, etc
>> reg = <0xf8000000 0x100000>;
>>
>> fpga_ic: [EMAIL PROTECTED] {
>> device_type = "fpga-int-ctlr";
>> interrupt-controller;
>> #address-cells = <0>;
>> #interrupt-cells = <2>;
>> interrupts = <2 26 3>; // IRQ2
BTW, this is wrong! Are the IRQ mappings on the MPC5200 documented
somewhere? I've looked and looked without much joy. Only by
experimentation did I discover that "<1 2 3>" corresponds to IRQ2.
>> interrupt-parent = <&mpc5200_pic>;
>> };
>> [EMAIL PROTECTED] {
>> compatible = "am,can";
>> device_type = "can";
>> interrupts = <0 0>;
>> interrupt_parent = <&fpga_ic>;
>> reg = <0xf8010000 0x200>;
>> };
>> };
>>
>> Of course, there will be more devices and interrupts later on,
>> this is just the first of many.
>
> Nothing obviously wrong so far other than you should use "compatible"
> properties to identify your devices, including (especially) the fpga &
> its pic, and maybe use slightly more verbose entries than "am,can" :-)
Fair enough, but these are 100% internal devices. I'm only using the
OF tree for them as that seems to be the accepted method (IMO, it's
a bit wrong-headed, but that's another discussion...)
>
>> Now the questions:
>> * How do I choose the VIRQ range supported by my FPGA?
>
> You don't. Linux virtual numbers are allocated sparsely and on the fly.
>
> You basically create an irq_host data structure, specifying what kind of
> reverse mapping you want (typically in your case I suspect linear since
> your HW interrupt space won't be huge), provide the appropriate
> callbacks, all I can suggest here is to look at what others do.
>
>> I'm interested in this in particular for the MPC5200, but
>> also for other chips (I have many such board configurations).
>> * How do I pass this information along to my drivers? I would
>> think that the interrupts value for the can interface above
>> would use a [logical] IRQ (an offset from the base VIRQ),
>> so how does the driver get the actual number (VIRQ+offset)
>> when probing the tree?
>
> Depends on the driver. But if they use an OF node, they can do
> of_irq_parse_and_map() or something like that. It will walk the tree,
> find the controller, map it to an irq_host (via the callbacks your
> provided), allocate a virq if not done yet, establish a virq->hw mapping
> etc... all for you, and return the virq.
>
This part is still a bit fuzzy. Where/how does my interrupt controller
driver get this VIRQ? Here's how I created my controller:
fpga_can_irq = irq_of_parse_and_map(fpga_ic, 0);
D_printk(("%s: fpga_irq = %d\n", __func__, (u32) fpga_can_irq));
if (fpga_can_irq == 0) {
printk(KERN_ERR "%s: Can't find FPGA Interrupt Controller IRQ",
__func__);
return -EINVAL;
}
if (request_irq(fpga_can_irq, &fpga_irq_cascade, 0, "FPGA CAN", 0)) {
printk(KERN_ERR "%s: Can't attach to FPGA Interrupt Controller IRQ",
__func__);
return -EINVAL;
}
fpga_irq_host = irq_alloc_host(of_node_get(fpga_node), IRQ_HOST_MAP_LINEAR,
16, &fpga_irq_host_ops, -1);
When I try to get the interrupt number for the CAN sub-device,
I always get zero :-(
for_each_compatible_node(np, "can", "am,can") {
memset(r, 0, sizeof(r));
rc = of_address_to_resource(np, 0, &r[0]);
if (rc) {
return rc;
}
rc = of_irq_to_resource(np, 0, &r[1]);
if (rc) {
return rc;
}
}
Note: the of_address_to_resource() call works fine, but the
of_irq_to_resource() fails - always returns 0. Any ideas what
I'm doing wrong?
> If they are PCI devices, the PCI code does it all for you.
Sadly, 100% home grown, not PCI.
>
>> * I know how to define the interrupt controller using irq_alloc_host()
>> (once I have the VIRQ range) but it's not clear to me where to stick
>> this initialization when bringing up my platform.
>
> You don't provide a virq range to irq_alloc_host. You provide a type of
> reverse mapping (depending on how sparse your HW numbering scheme is)
> and for a linear map, how many entries it contains (which is the size of
> your -physical- range).
>
> virqs are allocated on the fly.
>
Once I get the above call to work, I'll have to figure out how
to get at the VIRQ (so my cascade handler can signal the right
interrupt)
n.b. I only ask these questions after much investigation and
experimentation; I'm not asking you to do my job for me, just
help through the maze of twisty little passages!
--
------------------------------------------------------------
Gary Thomas | Consulting for the
MLB Associates | Embedded world
------------------------------------------------------------
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